Ta—Cu alloy material for extreme ultraviolet mask absorber

ABSTRACT

Extreme ultraviolet (EUV) mask blanks, methods for their manufacture and production systems therefor are disclosed. The EUV mask blanks comprise a substrate; a multilayer stack of reflective layers on the substrate; a capping layer on the multilayer stack of reflecting layers; and an absorber layer including an alloy of tantalum and copper on the capping layer.

TECHNICAL FIELD

The present disclosure relates generally to extreme ultravioletlithography, and more particularly extreme ultraviolet mask blanks withan absorber layer comprising an alloy of tantalum and copper, andmethods of manufacture.

BACKGROUND

Extreme ultraviolet (EUV) lithography, also known as soft x-rayprojection lithography, is used for the manufacture of 0.0135 micron andsmaller minimum feature size semiconductor devices. However, extremeultraviolet light, which is generally in the 5 to 100 nanometer (nm)wavelength range, is strongly absorbed in virtually all materials. Forthat reason, extreme ultraviolet systems work by reflection rather thanby transmission of light. Through the use of a series of mirrors, orlens elements, and a reflective element, or mask blank, coated with anon-reflective absorber mask pattern, the patterned actinic light isreflected onto a resist-coated semiconductor substrate.

The lens elements and mask blanks of extreme ultraviolet lithographysystems are coated with reflective multilayer coatings of materials suchas molybdenum and silicon. Reflection values of approximately 65% perlens element, or mask blank, have been obtained by using substrates thatare coated with multilayer coatings that strongly reflect light withinan extremely narrow ultraviolet bandpass, for example, 12.5 to 14.5 nmbandpass for 13.5 nm ultraviolet light.

FIG. 1 shows a conventional EUV reflective mask 10, which is formed froman EUV mask blank, which includes a reflective multilayer stack 12 on asubstrate 14, which reflects EUV radiation at unmasked portions by Bragginterference. Masked (non-reflective) areas 16 of the conventional EUVreflective mask 10 are formed by etching buffer layer 18 and absorbinglayer 20. The absorbing layer typically has a thickness in a range of 51nm to 77 nm. A capping layer 22 is formed over the reflective multilayerstack 12 and protects the reflective multilayer stack 12 during theetching process. As will be discussed further below, EUV mask blanks aremade on a low thermal expansion material substrate coated withmultilayers, capping layer and an absorbing layer, which is then etchedto provide the masked (non-reflective) areas 16 and reflective areas 24.

The International Technology Roadmap for Semiconductors (ITRS) specifiesa node's overlay requirement as some percentage of a technology'sminimum half-pitch feature size. Due to the impact on image placementand overlay errors inherent in all reflective lithography systems, EUVreflective masks will need to adhere to more precise flatnessspecifications for future production. Additionally, EUV blanks have avery low tolerance to defects on the working area of the blank. There isa need to provide EUV mask blanks having a thinner absorber to mitigate3D effects.

SUMMARY

One or more embodiments of the disclosure are directed to an extremeultraviolet (EUV) mask blank that includes a substrate, a multilayerstack of reflective layers on the substrate, the multilayer stack ofreflective layers including a plurality of reflective layers includingreflective layer pairs, a capping layer on the multilayer stack ofreflecting layers, and an absorber layer comprising an alloy of tantalumand copper.

Additional embodiments of the disclosure are directed to methods ofmanufacturing an extreme ultraviolet (EUV) mask blank that includeforming on a substrate a multilayer stack of reflective layers on thesubstrate, the multilayer stack of reflective layers including aplurality of reflective layer pairs, forming a capping layer on themultilayer stack of reflective layers, and forming an absorber layer onthe capping layer, the absorber layer comprising an alloy of tantalumand copper.

Additional embodiments of the disclosure are directed to an extremeultraviolet (EUV) EUV lithography system that includes an extremeultraviolet light source, and a reticle comprising a substrate, amultilayer stack over the substrate, and an absorber layer, over themultilayer stack, with a thickness of less than 80 nm and less than 2%reflectivity of an extreme ultraviolet (EUV) light at a wavelength of13.5 nm, wherein the absorber layer includes an alloy of tantalum andcopper.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 schematically illustrates a background art EUV reflective maskemploying a conventional absorber;

FIG. 2 schematically illustrates an embodiment of an extreme ultravioletlithography system;

FIG. 3 illustrates an embodiment of an extreme ultraviolet reflectiveelement production system;

FIG. 4 illustrates an embodiment of an extreme ultraviolet reflectiveelement such as an EUV mask blank;

FIG. 5 illustrates an embodiment of an extreme ultraviolet reflectiveelement such as an EUV mask blank; and

FIG. 6 illustrates an embodiment of a multi-cathode physical depositionchamber.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

The term “horizontal” as used herein is defined as a plane parallel tothe plane or surface of a mask blank, regardless of its orientation. Theterm “vertical” refers to a direction perpendicular to the horizontal asjust defined. Terms, such as “above”, “below”, “bottom”, “top”, “side”(as in “sidewall”), “higher”, “lower”, “upper”, “over”, and “under”, aredefined with respect to the horizontal plane, as shown in the figures.

The term “on” indicates that there is direct contact between elements.The term “directly on” indicates that there is direct contact betweenelements with no intervening elements.

As used in this specification according to one or more embodiments, theterms “precursor”, “reactant”, “reactive gas” and the like are usedinterchangeably to refer to any gaseous species that reacts with thesubstrate surface.

Those skilled in the art will understand that the use of ordinals suchas “first” and “second” to describe process regions do not imply aspecific location within the processing chamber, or order of exposurewithin the processing chamber.

As used in this specification and the appended claims, the term“substrate” refers to a surface, or portion of a surface, upon which aprocess acts. It will also be understood by those skilled in the artthat reference to a substrate in some embodiments refers to only aportion of the substrate, unless the context clearly indicatesotherwise. Additionally, reference to depositing on a substrate in someembodiments means both a bare substrate and a substrate with one or morefilms or features deposited or formed thereon.

Referring now to FIG. 2, an exemplary embodiment of an extremeultraviolet lithography system 100 is shown. The extreme ultravioletlithography system 100 includes an extreme ultraviolet light source 102for producing extreme ultraviolet light 112, a set of reflectiveelements, and a target wafer 110. The reflective elements include acondenser 104, an EUV reflective mask 106, an optical reduction assembly108, a mask blank, a mirror, or a combination thereof.

The extreme ultraviolet light source 102 generates the extremeultraviolet light 112. The extreme ultraviolet light 112 iselectromagnetic radiation having a wavelength in a range of 5 to 50nanometers (nm). For example, the extreme ultraviolet light source 102includes a laser, a laser produced plasma, a discharge produced plasma,a free-electron laser, synchrotron radiation, or a combination thereof.

The extreme ultraviolet light source 102 generates the extremeultraviolet light 112 having a variety of characteristics. The extremeultraviolet light source 102 produces broadband extreme ultravioletradiation over a range of wavelengths. For example, the extremeultraviolet light source 102 generates the extreme ultraviolet light 112having wavelengths ranging from 5 to 50 nm.

In one or more embodiments, the extreme ultraviolet light source 102produces the extreme ultraviolet light 112 having a narrow bandwidth.For example, the extreme ultraviolet light source 102 generates theextreme ultraviolet light 112 at 13.5 nm. The center of the wavelengthpeak is 13.5 nm.

The condenser 104 is an optical unit for reflecting and focusing theextreme ultraviolet light 112. The condenser 104 reflects andconcentrates the extreme ultraviolet light 112 from the extremeultraviolet light source 102 to illuminate the EUV reflective mask 106.

Although the condenser 104 is shown as a single element, it isunderstood that the condenser 104 in some embodiments includes one ormore reflective elements such as concave mirrors, convex mirrors, flatmirrors, or a combination thereof, for reflecting and concentrating theextreme ultraviolet light 112. For example, the condenser 104 in someembodiments is a single concave mirror or an optical assembly havingconvex, concave, and flat optical elements.

The EUV reflective mask 106 is an extreme ultraviolet reflective elementhaving a mask pattern 114. The EUV reflective mask 106 creates alithographic pattern to form a circuitry layout to be formed on thetarget wafer 110. The EUV reflective mask 106 reflects the extremeultraviolet light 112. The mask pattern 114 defines a portion of acircuitry layout.

The optical reduction assembly 108 is an optical unit for reducing theimage of the mask pattern 114. The reflection of the extreme ultravioletlight 112 from the EUV reflective mask 106 is reduced by the opticalreduction assembly 108 and reflected on to the target wafer 110. Theoptical reduction assembly 108 in some embodiments includes mirrors andother optical elements to reduce the size of the image of the maskpattern 114. For example, the optical reduction assembly 108 in someembodiments includes concave mirrors for reflecting and focusing theextreme ultraviolet light 112.

The optical reduction assembly 108 reduces the size of the image of themask pattern 114 on the target wafer 110. For example, the mask pattern114 in some embodiments is imaged at a 4:1 ratio by the opticalreduction assembly 108 on the target wafer 110 to form the circuitryrepresented by the mask pattern 114 on the target wafer 110. The extremeultraviolet light 112 of some embodiments scans the EUV reflective mask106 synchronously with the target wafer 110 to form the mask pattern 114on the target wafer 110.

Referring now to FIG. 3, an embodiment of an extreme ultravioletreflective element production system 200 is shown. The extremeultraviolet reflective element includes an EUV mask blank 204, anextreme ultraviolet mirror 205, or other reflective element such as anEUV reflective mask 106.

The extreme ultraviolet reflective element production system 200 in someembodiments produces mask blanks, mirrors, or other elements thatreflect the extreme ultraviolet light 112 of FIG. 2. The extremeultraviolet reflective element production system 200 fabricates thereflective elements by applying thin coatings to source substrates 203.

With reference to FIG. 3, the EUV mask blank 204 is a multilayeredstructure for forming the EUV reflective mask 106 of FIG. 2. The EUVmask blank 204 in some embodiments is formed using semiconductorfabrication techniques. The EUV reflective mask 106 of some embodimentshas the mask pattern 114 of FIG. 2 formed on the EUV mask blank 204 byetching and other processes.

The extreme ultraviolet mirror 205 is a multilayered structurereflective in a range of extreme ultraviolet light. The extremeultraviolet mirror 205 in some embodiments is formed using semiconductorfabrication techniques. The EUV mask blank 204 and the extremeultraviolet mirror 205 in some embodiments are similar structures withrespect to the layers formed on each element, however, the extremeultraviolet mirror 205 does not have the mask pattern 114.

The reflective elements are efficient reflectors of the extremeultraviolet light 112. In an embodiment, the EUV mask blank 204 and theextreme ultraviolet mirror 205 has an extreme ultraviolet reflectivityof greater than 60%. The reflective elements are generally consideredefficient if they reflect more than 60% of the extreme ultraviolet light112.

The extreme ultraviolet reflective element production system 200includes a wafer loading and carrier handling system 202 into which thesource substrates 203 are loaded and from which the reflective elementsare unloaded. An atmospheric handling system 206 provides access to awafer handling vacuum chamber 208. The wafer loading and carrierhandling system 202 in some embodiments include substrate transportboxes, loadlocks, and other components to transfer a substrate fromatmosphere to vacuum inside the system. Because the EUV mask blank 204is used to form devices at a very small scale, the source substrates 203and the EUV mask blank 204 are processed in a vacuum system to preventcontamination and other defects.

The wafer handling vacuum chamber 208 of some embodiments contains twovacuum chambers, a first vacuum chamber 210 and a second vacuum chamber212. The first vacuum chamber 210 includes a first wafer handling system214 and the second vacuum chamber 212 includes a second wafer handlingsystem 216. Although the wafer handling vacuum chamber 208 is describedwith two vacuum chambers, it is understood that the system of someembodiments has any number of vacuum chambers.

The wafer handling vacuum chamber 208 of some embodiments has aplurality of ports around its periphery for attachment of various othersystems. The first vacuum chamber 210 has a degas system 218, a firstphysical vapor deposition system 220, a second physical vapor depositionsystem 222, and a pre-clean system 224. The degas system 218 is forthermally desorbing moisture from the substrates. The pre-clean system224 is for cleaning the surfaces of the wafers, mask blanks, mirrors, orother optical components.

The physical vapor deposition systems, such as the first physical vapordeposition system 220 and the second physical vapor deposition system222, in some embodiments are used to form thin films of conductivematerials on the source substrates 203. For example, the physical vapordeposition systems in some embodiments include vacuum deposition systemsuch as magnetron sputtering systems, ion sputtering systems, pulsedlaser deposition, cathode arc deposition, or a combination thereof. Thephysical vapor deposition systems, such as the magnetron sputteringsystem, form thin layers on the source substrates 203 including thelayers of silicon, metals, alloys, compounds, or a combination thereof.

The physical vapor deposition system forms reflective layers, cappinglayers, and absorber layers. For example, the physical vapor depositionsystems of some embodiments forms layers of silicon, molybdenum,titanium oxide, titanium dioxide, ruthenium oxide, niobium oxide,ruthenium tungsten, ruthenium molybdenum, ruthenium niobium, chromium,tantalum, nitrides, compounds, or a combination thereof. Although somecompounds are described as an oxide, it is understood that the compoundsin some embodiments include oxides, dioxides, atomic mixtures havingoxygen atoms, or a combination thereof.

The second vacuum chamber 212 has a first multi-cathode source 226, achemical vapor deposition system 228, a cure chamber 230, and anultra-smooth deposition chamber 232 connected to it. For example, thechemical vapor deposition system 228 in some embodiments includes aflowable chemical vapor deposition system (FCVD), a plasma assistedchemical vapor deposition system (CVD), an aerosol assisted CVD, a hotfilament CVD system, or a similar system. In another example, thechemical vapor deposition system 228, the cure chamber 230, and theultra-smooth deposition chamber 232 in some embodiments are in aseparate system from the extreme ultraviolet reflective elementproduction system 200.

The chemical vapor deposition system 228 of some embodiments forms thinfilms of material on the source substrates 203. For example, thechemical vapor deposition system 228 in some embodiments is used to formlayers of materials on the source substrates 203 includingmono-crystalline layers, polycrystalline layers, amorphous layers,epitaxial layers, or a combination thereof. The chemical vapordeposition system 228 of some embodiments forms layers of silicon,silicon oxides, silicon oxycarbide, carbon, tungsten, silicon carbide,silicon nitride, titanium nitride, metals, alloys, and other materialssuitable for chemical vapor deposition. For example, the chemical vapordeposition system of some embodiments forms planarization layers.

The first wafer handling system 214 is capable of moving the sourcesubstrates 203 between the atmospheric handling system 206 and thevarious systems around the periphery of the first vacuum chamber 210 ina continuous vacuum. The second wafer handling system 216 is capable ofmoving the source substrates 203 around the second vacuum chamber 212while maintaining the source substrates 203 in a continuous vacuum. Theextreme ultraviolet reflective element production system 200 of someembodiments transfers the source substrates 203 and the EUV mask blank204 between the first wafer handling system 214, the second waferhandling system 216 in a continuous vacuum.

Referring now to FIG. 4, an embodiment of an extreme ultravioletreflective element 302 is shown. In one or more embodiments, the extremeultraviolet reflective element 302 is the EUV mask blank 204 of FIG. 3or the extreme ultraviolet mirror 205 of FIG. 3. The EUV mask blank 204and the extreme ultraviolet mirror 205 are structures for reflecting theextreme ultraviolet light 112 of FIG. 2. The EUV mask blank 204 in someembodiments is used to form the EUV reflective mask 106 shown in FIG. 2.

The extreme ultraviolet reflective element 302 includes a substrate 304,a multilayer stack 306 of reflective layers, and a capping layer 308. Inone or more embodiments, the extreme ultraviolet mirror 205 is used toform reflecting structures for use in the condenser 104 of FIG. 2 or theoptical reduction assembly 108 of FIG. 2.

The extreme ultraviolet reflective element 302, which in someembodiments is an EUV mask blank 204, includes the substrate 304, themultilayer stack 306 of reflective layers, the capping layer 308, and anabsorber layer 310. The extreme ultraviolet reflective element 302 insome embodiments is an EUV mask blank 204, which is used to form the EUVreflective mask 106 of FIG. 2 by patterning the absorber layer 310 withthe layout of the circuitry required. The absorber layer in certainembodiments is coated with an antireflective coating (not shown), suchas an anti-reflective coating selected from, for example, tantalumoxynitride and tantalum boron oxide.

In the following sections, the term for the EUV mask blank 204 is usedinterchangeably with the term of the extreme ultraviolet mirror 205 forsimplicity. In one or more embodiments, the EUV mask blank 204 includesthe components of the extreme ultraviolet mirror 205 with the absorberlayer 310 added in addition to form the mask pattern 114 of FIG. 2.

The EUV mask blank 204 is an optically flat structure used for formingthe EUV reflective mask 106 having the mask pattern 114, which in someembodiments represents a processing layer of an integrated circuit. Thereflective mask 106, once fully processed, in some embodiments isreferred to as a reticle. In one or more embodiments, the reflectivesurface of the EUV mask blank 204 forms a flat focal plane forreflecting the incident light, such as the extreme ultraviolet light 112of FIG. 2.

With reference to FIG. 4, the substrate 304 is an element for providingstructural support to the extreme ultraviolet reflective element 302. Inone or more embodiments, the substrate 304 is made from a materialhaving a low coefficient of thermal expansion (CTE) to provide stabilityduring temperature changes. In one or more embodiments, the substrate304 has properties such as stability against mechanical cycling, thermalcycling, crystal formation, or a combination thereof. The substrate 304according to one or more embodiments is formed from a material such as,for example, silicon, glass, oxides, ceramics, glass ceramics, or acombination thereof.

The multilayer stack 306 is a structure that is reflective to theextreme ultraviolet light 112. The multilayer stack 306 includesalternating reflective layers of a first reflective layer 312 and asecond reflective layer 314.

The first reflective layer 312 and the second reflective layer 314 forma reflective pair 316 of FIG. 4. In a non-limiting embodiment, themultilayer stack 306 includes a range of 20-60 of the reflective pairs316 for a total of up to 120 reflective layers.

The first reflective layer 312 and the second reflective layer 314 insome embodiments are formed from a variety of materials. In anembodiment, the first reflective layer 312 and the second reflectivelayer 314 are formed from silicon and molybdenum, respectively. Althoughthe layers are shown as silicon and molybdenum, it is understood thatthe alternating layers in some embodiments are formed from othermaterials or have other internal structures.

The first reflective layer 312 and the second reflective layer 314 ofsome embodiments have a variety of structures. In an embodiment, boththe first reflective layer 312 and the second reflective layer 314 areformed with a single layer, multiple layers, a divided layer structure,non-uniform structures, or a combination thereof.

Because most materials absorb light at extreme ultraviolet wavelengths,the optical elements used are reflective, instead of the transmissive asused in other lithography systems. The multilayer stack 306 forms areflective structure by having alternating thin layers of materials withdifferent optical properties to create a Bragg reflector or mirror.

In an embodiment, each of the alternating layers has dissimilar opticalconstants for the extreme ultraviolet light 112. The alternating layersprovide a resonant reflectivity when the period of the thickness of thealternating layers is one half the wavelength of the extreme ultravioletlight 112. In an embodiment, for the extreme ultraviolet light 112 at awavelength of 13 nm, the alternating layers are about 6.5 nm thick. Itis understood that the sizes and dimensions provided are within normalengineering tolerances for typical elements.

The multilayer stack 306 in some embodiments is formed in a variety ofways. In an embodiment, the first reflective layer 312 and the secondreflective layer 314 are formed with magnetron sputtering, ionsputtering systems, pulsed laser deposition, cathode arc deposition, ora combination thereof.

In an illustrative embodiment, the multilayer stack 306 is formed usinga physical vapor deposition technique, such as magnetron sputtering. Inan embodiment, the first reflective layer 312 and the second reflectivelayer 314 of the multilayer stack 306 have the characteristics of beingformed by the magnetron sputtering technique including precisethickness, low roughness, and clean interfaces between the layers. In anembodiment, the first reflective layer 312 and the second reflectivelayer 314 of the multilayer stack 306 have the characteristics of beingformed by the physical vapor deposition including precise thickness, lowroughness, and clean interfaces between the layers.

The physical dimensions of the layers of the multilayer stack 306 formedusing the physical vapor deposition technique in some embodiments areprecisely controlled to increase reflectivity. In an embodiment, thefirst reflective layer 312, such as a layer of silicon, has a thicknessof 4.1 nm. The second reflective layer 314, such as a layer ofmolybdenum, has a thickness of 2.8 nm. The thickness of the layersdictates the peak reflectivity wavelength of the extreme ultravioletreflective element. If the thickness of the layers is incorrect, thereflectivity at the desired wavelength 13.5 nm in some embodiments isreduced.

In an embodiment, the multilayer stack 306 has a reflectivity of greaterthan 60%. In an embodiment, the multilayer stack 306 formed usingphysical vapor deposition has a reflectivity in a range of 66%-67%. Inone or more embodiments, forming the capping layer 308 over themultilayer stack 306 formed with harder materials improves reflectivity.In some embodiments, reflectivity greater than 70% is achieved using lowroughness layers, clean interfaces between layers, improved layermaterials, or a combination thereof.

In one or more embodiments, the capping layer 308 is a protective layerallowing the transmission of the extreme ultraviolet light 112. In anembodiment, the capping layer 308 is formed directly on the multilayerstack 306. In one or more embodiments, the capping layer 308 protectsthe multilayer stack 306 from contaminants and mechanical damage. In oneembodiment, the multilayer stack 306 is sensitive to contamination byoxygen, carbon, hydrocarbons, or a combination thereof. The cappinglayer 308 according to an embodiment interacts with the contaminants toneutralize them.

In one or more embodiments, the capping layer 308 is an opticallyuniform structure that is transparent to the extreme ultraviolet light112. The extreme ultraviolet light 112 passes through the capping layer308 to reflect off of the multilayer stack 306. In one or moreembodiments, the capping layer 308 has a total reflectivity loss of 1%to 2%. In one or more embodiments, each of the different materials has adifferent reflectivity loss depending on thickness, but all of them willbe in a range of 1% to 2%.

In one or more embodiments, the capping layer 308 has a smooth surface.For example, the surface of the capping layer 308 of some embodimentshas a roughness of less than 0.2 nm RMS (root mean square measure). Inanother example, the surface of the capping layer 308 has a roughness of0.08 nm RMS for a length in a range of 1/100 nm and 1/1 μm. The RMSroughness will vary depending on the range over which it is measured.For the specific range of 100 nm to 1 micron that roughness is 0.08 nmor less. Over a larger range, the roughness will be higher.

The capping layer 308 in some embodiments is formed in a variety ofmethods. In an embodiment, the capping layer 308 is formed on ordirectly on the multilayer stack 306 with magnetron sputtering, ionsputtering systems, ion beam deposition, electron beam evaporation,radio frequency (RF) sputtering, atomic layer deposition (ALD), pulsedlaser deposition, cathode arc deposition, or a combination thereof. Inone or more embodiments, the capping layer 308 has the physicalcharacteristics of being formed by the magnetron sputtering techniqueincluding precise thickness, low roughness, and clean interfaces betweenthe layers. In an embodiment, the capping layer 308 has the physicalcharacteristics of being formed by the physical vapor depositionincluding precise thickness, low roughness, and clean interfaces betweenthe layers.

In one or more embodiments, the capping layer 308 is formed from avariety of materials having a hardness sufficient to resist erosionduring cleaning. In one embodiment, ruthenium is used as a capping layermaterial because it is a good etch stop and is relatively inert underthe operating conditions. However, it is understood that other materialsin some embodiments are used to form the capping layer 308. In specificembodiments, the capping layer 308 has a thickness in a range of 2.5 and5.0 nm.

In one or more embodiments, the absorber layer 310 is a layer thatabsorbs the extreme ultraviolet light 112. In an embodiment, theabsorber layer 310 is used to form the pattern on the EUV reflectivemask 106 by providing areas that do not reflect the extreme ultravioletlight 112. The absorber layer 310, according to one or more embodiments,comprises a material having a high absorption coefficient for aparticular frequency of the extreme ultraviolet light 112, such as about13.5 nm. In an embodiment, the absorber layer 310 is formed directly onthe capping layer 308, and the absorber layer 310 is etched using aphotolithography process to form the pattern of the EUV reflective mask106.

According to one or more embodiments, the extreme ultraviolet reflectiveelement 302, such as the extreme ultraviolet mirror 205, is formed withthe substrate 304, the multilayer stack 306, and the capping layer 308.The extreme ultraviolet mirror 205 has an optically flat surface and insome embodiments efficiently and uniformly reflects the extremeultraviolet light 112.

According to one or more embodiments, the extreme ultraviolet reflectiveelement 302, such as the EUV mask blank 204, is formed with thesubstrate 304, the multilayer stack 306, the capping layer 308, and theabsorber layer 310. The mask blank 204 has an optically flat surface andin some embodiments efficiently and uniformly reflects the extremeultraviolet light 112. In an embodiment, the mask pattern 114 is formedwith the absorber layer 310 of the EUV mask blank 204.

According to one or more embodiments, forming the absorber layer 310over the capping layer 308 increases reliability of the EUV reflectivemask 106. The capping layer 308 acts as an etch stop layer for theabsorber layer 310. When the mask pattern 114 of FIG. 2 is etched intothe absorber layer 310, the capping layer 308 beneath the absorber layer310 stops the etching action to protect the multilayer stack 306. In oneor more embodiments, the absorber layer 310 is etch selective to thecapping layer 308. In some embodiments, the capping layer 308 comprisesruthenium, and the absorber layer 310 is etch selective to ruthenium.

In one embodiment, the absorber layer 310 comprises an alloy of tantalumand copper. The alloy of tantalum and copper according to someembodiments is provided as a single phase. In one embodiment, the alloyof tantalum (Ta) and copper (Cu) is provided as an amorphous film. Theabsorber layer 310 in certain embodiments further includes an additionallayer of tantalum and/or an additional layer of copper (not shown).

In one embodiment, an absorber layer 310 comprises an alloy of tantalumand copper as a single layer, and has a thickness of less than about 45nm. In some embodiments, the absorber layer has a thickness of less thanabout 40 nm, less than about 35 nm, less than about 30 nm, less thanabout 25 nm, less than about 20 nm, less than about 15 nm, less thanabout 10 nm, less than about 5 nm, less than about 1 nm, or less thanabout 0.5 nm. In other embodiments, the absorber layer 310 has athickness in a range of about 0.5 nm to about 45 nm, including a rangeof about 1 nm to about 44 nm, 1 nm to about 40 nm, and 15 nm to about 40nm. While not intending to be bound by any particular theory, anabsorber layer 310 having a thickness of less than about 45 nmadvantageously results in an absorber layer having a reflectively ofless than about 2% (e.g., less than 2% reflectivity when deposited on40XML/Ru), reducing and mitigating 3D effects in the extreme ultraviolet(EUV) mask blank. The alloy of tantalum and copper, in certainembodiments, possess a high cleaning durability and defect repair takesplace.

In an alternative embodiment, multiple absorber layers are provided inplace of absorber layer 310, in which one of the multiple absorberlayers is an alloy of tantalum and copper. In one embodiment, theextreme ultraviolet (EUV) mask blank includes alternating absorberlayers (i.e., alternative layers of an absorber layer and a secondabsorber layer). In one embodiment, the extreme ultraviolet (EUV) maskblank includes a multilayer absorber that include alternating layers ofTiN and an alloy of tantalum and copper. In one embodiment, thethickness of the TiN layer is from about 1 nm to about 40 nm, or fromabout 1 nm to about 30 nm, or from about 1 nm to about 20 nm, or fromabout 1 nm to about 10 nm (e.g., 2.0 nm). The thickness of the alloy oftantalum and copper layer are is as described herein.

In a specific embodiment, the alloy of tantalum and copper is a tantalumrich alloy. As used herein, the term “tantalum rich” means that there isat least an equal amount of tantalum in the alloy than copper, or agreater amount of tantalum in the alloy than copper. For example, in aspecific embodiment, the tantalum rich alloy of tantalum and copper isan alloy having from about 50 wt. % to about 85 wt. % tantalum and fromabout 15 wt. % to about 50 wt. % copper. In another specific embodiment,the alloy of tantalum and copper is an alloy having from about 54.4 wt.% to about 80.0 wt. % tantalum and from about 20 wt. % and about 45.6wt. % copper. In another specific embodiment, the alloy of tantalum andcopper is an alloy having from about 60.5 wt. % to about 72.7 wt. %tantalum and from about 27.3 wt. % to about 39.5 wt. % copper. Inanother specific embodiment, the alloy of tantalum and copper is analloy having from about 54.4 wt. % to about 66.5 wt. % tantalum and fromabout 33.4 wt. % to about 45.6 wt. % copper. In another specificembodiment, the alloy of tantalum and copper is an alloy having fromabout 66.5 wt. % to about 80 wt. % tantalum and from about 20 wt. % toabout 33.4 wt. % copper. In one embodiment, the alloy of tantalum andcopper is an alloy having about 60.5 wt. % tantalum and about 39.5 wt. %copper. In one embodiment, the alloy of tantalum and copper is an alloyhaving about 72.7 wt. % tantalum and about 27.3 wt. % copper. All weightpercentages (wt. %) based upon the total weight of the alloy.

In a still further specific embodiment, the alloy of tantalum and copperis a copper rich alloy. As used herein, the term “copper rich” meansthat there is a greater amount of copper in the alloy than tantalum. Forexample, in a specific embodiment, the copper rich alloy of tantalum andcopper is an alloy having from about 65 wt. % to about 95 wt. % copperand from about 5 wt. % to about 35 wt. % tantalum. In one embodiment,the alloy of tantalum and copper is an alloy having from about 78.8 wt.% to about 85 wt. % copper and from about 15 wt. % to about 21.2 wt. %tantalum. In one embodiment, the alloy of tantalum and copper is analloy having from about 80.7 wt. % to about 83.3 wt. % copper and fromabout 16.7 wt. % to about 19.3 wt. % tantalum. In one embodiment, thealloy of tantalum and copper is an alloy having from about 81.63 wt. %to about 85 wt. % copper and from about 15 wt. % to about 18.4 wt. %tantalum. In one embodiment, the alloy of tantalum and copper is analloy having from about 78.8 wt. % to about 81.63 wt. % copper and fromabout 18.4 wt. % to about 21.2 wt. % tantalum. In one embodiment, thealloy of tantalum and copper is an alloy having about 83.3 wt. % copperand about 16.7 wt. % tantalum. In one embodiment, the alloy of tantalumand copper is an alloy having about 80.7 wt. % copper and about 19.3 wt.% tantalum. All weight percentages (wt. %) are based upon the totalweight of the alloy.

In one or more embodiments, the alloy of tantalum and copper comprises adopant. The dopant may be selected from one or more of nitrogen oroxygen. In an embodiment, the dopant comprises oxygen. In an alternativeembodiment, the dopant comprises nitrogen. In an embodiment, the dopantis present in the alloy in an amount in the range of about 0.1 wt. % toabout 5 wt. %, based upon the weight of the alloy. In other embodiments,the dopant is present in the alloy in an amount of about 0.1 wt. %, 0.2wt. %, 0.3 wt. %, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %. 0.8 wt. %,0.9 wt. %, 1.0 wt. %, 1.1 wt. %, 1.2 wt. %, 1.3 wt. %, 1.4 wt. %, 1.5wt. %, 1.6 wt. %, 1.7 wt. %. 1.8 wt. %, 1.9 wt. %, 2.0 wt. % 2.1 wt. %,2.2 wt. %, 2.3 wt. %, 2.4 wt. %, 2.5 wt. %, 2.6 wt. %, 2.7 wt. %. 2.8wt. %, 2.9 wt. %, 3.0 wt. %, 3.1 wt. %, 3.2 wt. %, 3.3 wt. %, 3.4 wt. %,3.5 wt. %, 3.6 wt. %, 3.7 wt. %. 3.8 wt. %, 3.9 wt. %, 4.0 wt. %, 4.1wt. %, 4.2 wt. %, 4.3 wt. %, 4.4 wt. %, 4.5 wt. %, 4.6 wt. %, 4.7 wt. %.4.8 wt. %, 4.9 wt. %, or 5.0 wt. %, based upon the weight of the alloy.

In one or more embodiments, the absorber layer is co-sputtered in aphysical deposition chamber, which provides much thinner absorber layerthickness (e.g., less than 45 nm or less than 30 nm) while achievingless than 2% reflectivity and suitable etch properties. In one or moreembodiments, the alloy of tantalum and copper of the absorber layer isco-sputtered by gases selected from one or more of argon (Ar), oxygen(O₂), or nitrogen (N₂). In an embodiment, the alloy of tantalum andcopper of the absorber layer is co-sputtered by a mixture of argon andoxygen gases (Ar+O₂). In some embodiments, co-sputtering by a mixture ofargon and oxygen forms and oxide of copper and/or an oxide of tantalum.In other embodiments, co-sputtering by a mixture of argon and oxygendoes not form an oxide of copper or tantalum. In an embodiment, thealloy of tantalum and copper of the absorber layer is co-sputtered by amixture of argon and nitrogen gases (Ar+N₂). In some embodiments,co-sputtering by a mixture of argon and nitrogen forms a nitride ofcopper and/or a nitride of tantalum. In other embodiments, co-sputteringby a mixture of argon and nitrogen does not form a nitride of copper ortantalum. In an embodiment, the alloy of the absorber layer isco-sputtered by a mixture of argon and oxygen and nitrogen gases(Ar+O₂+N₂). In some embodiments, co-sputtering by a mixture of argon andoxygen and nitrogen forms an oxide and/or nitride of copper and/or anoxide and/or nitride of tantalum. In other embodiments, co-sputtering bya mixture of argon and oxygen and nitrogen does not form an oxide or anitride of copper or tantalum. In an embodiment, the etch propertiesand/or other properties of the absorber layer are tailored tospecification by controlling the alloy percentage(s), as discussedabove. In an embodiment, the alloy percentage(s) are preciselycontrolled by operating parameters such voltage, pressure, flow, etc.,of the physical vapor deposition chamber. In an embodiment, a processgas is used to further modify the material properties, for example, N₂gas is used to form nitrides of tantalum and copper.

In one or more embodiments, as used herein “co-sputtering” means thattwo targets, one target comprising copper and the second targetcomprising tantalum are sputtered at the same time using one or more gasselected from argon (Ar), oxygen (O₂), or nitrogen (N₂) to deposit/forman absorber layer comprising an alloy of tantalum and copper.

In other embodiments, tantalum and copper are deposited layer by layeras a laminate of tantalum and copper layers using gases selected fromone or more of argon (Ar), oxygen (O₂), or nitrogen (N₂). In anembodiment, tantalum and copper are deposited layer by layer as alaminate of tantalum and copper layers using a mixture of argon andoxygen gases (Ar+O₂). In some embodiments, tantalum and copper aredeposited layer by layer as a laminate of tantalum and copper layersusing a mixture of argon and oxygen and forms an oxide of copper and/oran oxide of tantalum. In other embodiments, layer by layer depositionusing a mixture of argon and oxygen does not form an oxide of copper ortantalum. In an embodiment, tantalum and copper are deposited layer bylayer as a laminate of tantalum and copper layers using a mixture ofargon and nitrogen gases (Ar+N₂). In some embodiments, layer by layerdeposition using a mixture of argon and nitrogen forms a nitride ofcopper and/or a nitride of tantalum. In other embodiments, layer bylayer deposition using a mixture of argon and nitrogen does not form anitride of copper or tantalum. In an embodiment, tantalum and copper aredeposited layer by layer as a laminate of tantalum and copper layersusing a mixture of argon and oxygen and nitrogen gases (Ar+O₂+N₂). Insome embodiments, layer by layer depositing using a mixture of argon andoxygen and nitrogen forms an oxide and/or nitride of copper and/or anoxide and/or nitride of tantalum. In other embodiments, layer by layerdeposition using a mixture of argon and oxygen and nitrogen does notform an oxide or a nitride of copper or tantalum.

In one or more embodiments, bulk targets of the alloy compositionsdescribed herein are made, which are sputtered by normal sputteringusing gases selected from one or more of argon (Ar), oxygen (O₂), ornitrogen (N₂). In one or more embodiments, the alloy is deposited usinga bulk target having the same composition as the alloy and is sputteredusing a gas selected from one or more of argon (Ar), oxygen (O₂), ornitrogen (N₂) to form the absorber layer. In one particular embodiment,the alloy of the absorber layer is deposited using a bulk target havingthe same composition of the alloy and is sputtered using a mixture ofargon and oxygen gases (Ar+O₂). In some embodiments, bulk targetdeposition using a mixture of argon and oxygen forms an oxide of copperand/or an oxide of tantalum. In other embodiments, bulk targetdeposition using a mixture of argon and oxygen does not form an oxide ofcopper or tantalum. In an embodiment, the alloy of the absorber layer isdeposited using a bulk target having the same composition of the alloyand is sputtered using a mixture of argon and nitrogen gases (Ar+N₂). Insome embodiments, bulk target deposition using a mixture of argon andnitrogen forms a nitride of copper and/or a nitride of tantalum. Inother embodiments, bulk target deposition using a mixture of argon andnitrogen does not form a nitride of copper or tantalum. In anembodiment, the alloy of the absorber layer is deposited using a bulktarget having the same composition of the alloy and is sputtered using amixture of argon and oxygen and nitrogen gases (Ar+O₂+N₂). In someembodiments, bulk target depositing using a mixture of argon and oxygenand nitrogen forms an oxide and/or nitride of copper and/or an oxideand/or nitride of tantalum. In other embodiments, bulk target depositionusing a mixture of argon and oxygen and nitrogen does not form an oxideor a nitride of copper or tantalum.

Referring now to FIG. 5, an extreme ultraviolet mask blank 400 is shownas comprising a substrate 414, a multilayer stack of reflective layers412 on the substrate 414, the multilayer stack of reflective layers 412including a plurality of reflective layer pairs. In one or moreembodiments, the plurality of reflective layer pairs are made from amaterial selected from a molybdenum (Mo) containing material and silicon(Si) containing material. In some embodiments, the plurality ofreflective layer pairs comprises alternating layers of molybdenum andsilicon. The extreme ultraviolet mask blank 400 further includes acapping layer 422 on the multilayer stack of reflective layers 412, andthere is a multilayer stack 420 of absorber layers on the capping layer422. In one or more embodiment, the plurality of reflective layers 412are selected from a molybdenum (Mo) containing material and a silicon(Si) containing material and the capping layer 422 comprises ruthenium.

The multilayer stack 420 of absorber layers includes a plurality ofabsorber layer pairs 420 a, 420 b, 420 c, 420 d, 420 e, 420 f, each pair(420 a/420 b, 420 c/420 d, 420 e/420 f) comprising an alloy of tantalumand copper. In some embodiments, the alloy of tantalum and copper is atantalum rich alloy, or alternatively, a copper rich alloy, such as anyone of the alloys of tantalum and copper described herein.

For example, in one exemplary embodiment, absorber layer 420 a is madefrom a tantalum material and the material that forms absorber layer 420b is an alloy of tantalum and copper. Likewise, absorber layer 420 c ismade from a tantalum material and the material that forms absorber layer420 d is an alloy of tantalum and copper, and absorber layer 420 e ismade from a tantalum material and the material that forms absorber layer420 f is an alloy of tantalum and copper.

According to one or more embodiments, the absorber layer pairs comprisea first layer (420 a, 420 c, 420 e) and a second absorber layer (420 b,420 d, 420 f) each of the first absorber layers (420 a, 420 c, 420 e)and second absorber layer (420 b, 420 d, 420 f) have a thickness in arange of 0.1 nm and 10 nm, for example in a range of 1 nm and 5 nm, orin a range of 1 nm and 3 nm. In one or more specific embodiments, thethickness of the first layer 420 a is 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm,0.9 nm, 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm,1.8 nm, 1.9 nm, 2 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, 2.6 nm,2.7 nm, 2.8 nm, 2.9 nm, 3 nm, 3.1 nm, 3.2 nm, 3.3 nm, 3.4 nm, 3.5 nm,3.6 nm, 3.7 nm, 3.8 nm, 3.9 nm, 4 nm, 4.1 nm, 4.2 nm, 4.3 nm, 4.4 nm,4.5 nm, 4.6 nm, 4.7 nm, 4.8 nm, 4.9 nm, and 5 nm. In one or moreembodiments, the thickness of the first absorber layer and secondabsorber layer of each pair is the same or different. For example, thefirst absorber layer and second absorber layer have a thickness suchthat there is a ratio of the first absorber layer thickness to secondabsorber layer thickness of 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1,4.5:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1,16:1, 17:1, 18:1, 19:1, or 20:1, which results in the first absorberlayer having a thickness that is equal to or greater than the secondabsorber layer thickness in each pair. Alternatively, the first absorberlayer and second absorber layer have a thickness such that there is aratio of the second absorber layer thickness to first absorber layerthickness of 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 6:1, 7:1,8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or20:1 which results in the second absorber layer having a thickness thatis equal to or greater than the first absorber layer thickness in eachpair.

According to one or more embodiments, the different absorber materialsand thickness of the absorber layers are selected so that extremeultraviolet light is absorbed due to absorbance and due to a phasechange caused by destructive interfere with light from the multilayerstack of reflective layers. While the embodiment shown in FIG. 5 showsthree absorber layer pairs, 420 a/420 b, 420 c/420 d and 420 e/420 f,the claims should not be limited to a particular number of absorberlayer pairs. According to one or more embodiments, the EUV mask blank400 includes in a range of 5 and 60 absorber layer pairs or in a rangeof 10 and 40 absorber layer pairs.

According to one or more embodiments, the absorber layer(s) have athickness which provides less than 2% reflectivity and other etchproperties. A supply gas in some embodiments is used to further modifythe material properties of the absorber layer(s), for example, nitrogen(N₂) gas is used to form nitrides of the materials provided above. Themultilayer stack of absorber layer(s) according to one or moreembodiments is a repetitive pattern of individual thickness of differentmaterials so that the EUV light not only gets absorbed due toabsorbance, but by the phase change caused by multilayer absorber stack,which will destructively interfere with light from multilayer stack ofreflective materials beneath to provide better contrast.

Another aspect of the disclosure pertains to a method of manufacturingan extreme ultraviolet (EUV) mask blank comprising forming on asubstrate a multilayer stack of reflective layers on the substrate, themultilayer stack including a plurality of reflective layer pairs,forming a capping layer on the multilayer stack of reflective layers,and forming absorber layer on the capping layer, the absorber layercomprising an alloy of tantalum and copper, such as any one of thealloys described herein.

The EUV mask blank in some embodiments has any of the characteristics ofthe embodiments described above with respect to FIG. 4 and FIG. 5, andthe method of some embodiments is performed in the system described withrespect to FIG. 3.

Referring now to FIG. 6 an upper portion of a multi-cathode sourcechamber 500 is shown in accordance with one particular embodiment. Themulti-cathode chamber 500 includes a base structure 501 with acylindrical body portion 502 capped by a top adapter 504. The topadapter 504 has provisions for a number of cathode sources, such ascathode sources 506, 508, 510, 512, and 514, positioned around the topadapter 504.

The multi-cathode source chamber 500 in some embodiments is part of thesystem shown in FIG. 3. In an embodiment, an extreme ultraviolet (EUV)mask blank production system comprises a substrate handling vacuumchamber for creating a vacuum, a substrate handling platform, in thevacuum, for transporting a substrate loaded in the substrate handlingvacuum chamber, and multiple sub-chambers, accessed by the substratehandling platform, for forming an EUV mask blank, including a multilayerstack of reflective layers on the substrate, the multilayer stackincluding a plurality of reflective layer pairs, a capping layer on themultilayer stack of reflective layers, and an absorber layer on thecapping layer, the absorber layer made from tantalum and an alloy oftantalum and copper. The system in some embodiments is used to make theEUV mask blanks shown with respect to FIG. 4 or FIG. 5 and have any ofthe properties described with respect to the EUV mask blanks describedwith respect to FIG. 4 or FIG. 5 above.

Processes may generally be stored in the memory as a software routinethat, when executed by the processor, causes the process chamber toperform processes of the present disclosure. The software routine mayalso be stored and/or executed by a second processor (not shown) that isremotely located from the hardware being controlled by the processor.Some or all of the method of the present disclosure may also beperformed in hardware. As such, the process may be implemented insoftware and executed using a computer system, in hardware as, e.g., anapplication specific integrated circuit or other type of hardwareimplementation, or as a combination of software and hardware. Thesoftware routine, when executed by the processor, transforms the generalpurpose computer into a specific purpose computer (controller) thatcontrols the chamber operation such that the processes are performed.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. An extreme ultraviolet (EUV) mask blankcomprising: a substrate; a multilayer stack of reflective layers on thesubstrate, the multilayer stack of reflective layers including aplurality of reflective layers including reflective layer pairs; acapping layer on the multilayer stack of reflecting layers; and anabsorber layer comprising an alloy of tantalum and copper.
 2. Theextreme ultraviolet (EUV) mask blank of claim 1, wherein the alloy oftantalum and copper is a tantalum rich alloy comprising from about 50 toabout 85 wt. % tantalum and from about 15 to about 50 wt. % copper. 3.The extreme ultraviolet (EUV) mask blank of claim 2, wherein thetantalum rich alloy comprises from about 60.5 to about 72.7 wt. %tantalum and from about 27.3 to about 39.5 wt. % copper.
 4. The extremeultraviolet (EUV) mask blank of claim 1, wherein the alloy of tantalumand copper is a copper rich alloy comprising from about 65 to about 95wt. % copper and from about 5 to about 35 wt. % tantalum.
 5. The extremeultraviolet (EUV) mask blank of claim 4, wherein the copper rich alloycomprises from about 80.7 to about 83.3 wt. % copper and from about 27.3to about 39.5 wt. % tantalum.
 6. The extreme ultraviolet (EUV) maskblank of claim 1, wherein the absorber layer has a thickness of lessthan 45 nm.
 7. The extreme ultraviolet (EUV) mask blank of claim 1,wherein the absorber layer has a reflectivity of less than about 2% andis etch selective relative to the capping layer.
 8. The extremeultraviolet (EUV) mask blank of claim 1, wherein the absorber layerfurther comprises 0.1 wt. % to about 5 wt. % of a dopant selected fromone or more of nitrogen or oxygen.
 9. The extreme ultraviolet (EUV) maskblank of claim 1, further comprising a second absorber layer thatincludes TiN.
 10. A method of manufacturing an extreme ultraviolet (EUV)mask blank comprising: providing a substrate; forming a multilayer stackof reflective layers on the substrate, the multilayer stack ofreflective layers including a plurality of reflective layer pairs;forming a capping layer on the multilayer stack of reflective layers;and forming an absorber layer on the capping layer, the absorber layercomprising an alloy of tantalum and copper.
 11. The method of claim 10,wherein the alloy of tantalum and copper is a tantalum rich alloycomprising from about 50 to about 85 wt. % tantalum and from about 15 toabout 50 wt. % copper.
 12. The method of claim 11, wherein the tantalumrich alloy comprises from about 60.5 to about 72.7 wt. % tantalum andfrom about 27.3 to about 39.5 wt. % copper.
 13. The method of claim 10,wherein the alloy of tantalum and copper is a copper rich alloycomprising from about 65 to about 95 wt. % copper and from about 5 toabout 35 wt. % tantalum.
 14. The method of claim 13, wherein the copperrich alloy comprises from about 80.7 to about 83.3 wt. % copper and fromabout 27.3 to about 39.5 wt. % tantalum.
 15. The method of claim 10,wherein the alloy of tantalum and copper is co-sputtered by a gasselected from one or more of argon (Ar), oxygen (O₂), or nitrogen (N₂)to form the absorber layer.
 16. The method of claim 10, wherein thealloy of tantalum and copper is deposited using a bulk target having asame composition as the alloy of tantalum and copper and is sputteredusing a gas selected from one or more of argon (Ar), oxygen (O₂), ornitrogen (N₂) to form the absorber layer.
 17. An extreme ultraviolet(EUV) lithography system comprising: an extreme ultraviolet lightsource; and a reticle comprising a substrate, the reticle having apattern that represents a processing layer of an integrated circuit; amultilayer stack over the substrate; and an absorber layer, over themultilayer stack, with a thickness of less than 80 nm and less than 2%reflectivity of an extreme ultraviolet (EUV) light at a wavelength of13.5 nm, wherein the absorber layer includes an alloy of tantalum andcopper.
 18. The system as claimed in claim 17 further comprising acapping layer between the multilayer stack and the absorber layer, forprotecting the multilayer stack.
 19. The system as claimed in claim 17wherein the reticle has a pattern that represents a processing layer ofan integrated circuit.
 20. The system as claimed in claim 17, furthercomprising an anti-reflective coating on the absorber layer.